EP0871865B1 - Device for measuring the partial pressure of gases dissolved in liquids - Google Patents

Device for measuring the partial pressure of gases dissolved in liquids Download PDF

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Publication number
EP0871865B1
EP0871865B1 EP95942708A EP95942708A EP0871865B1 EP 0871865 B1 EP0871865 B1 EP 0871865B1 EP 95942708 A EP95942708 A EP 95942708A EP 95942708 A EP95942708 A EP 95942708A EP 0871865 B1 EP0871865 B1 EP 0871865B1
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European Patent Office
Prior art keywords
measuring
gas
light
measuring chamber
membrane
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EP95942708A
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German (de)
French (fr)
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EP0871865A2 (en
Inventor
Michael Dieckmann
Rainer Buchholz
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Euroferm Gesellschaft fur Fermentation und Messtechnik Mbh
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Euroferm Gesellschaft fur Fermentation und Messtechnik Mbh
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
    • G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
    • G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M41/00—Means for regulation, monitoring, measurement or control, e.g. flow regulation
    • C12M41/30—Means for regulation, monitoring, measurement or control, e.g. flow regulation of concentration
    • C12M41/32—Means for regulation, monitoring, measurement or control, e.g. flow regulation of concentration of substances in solution
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M41/00—Means for regulation, monitoring, measurement or control, e.g. flow regulation
    • C12M41/40—Means for regulation, monitoring, measurement or control, e.g. flow regulation of pressure
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/85—Investigating moving fluids or granular solids
    • G01N21/8507—Probe photometers, i.e. with optical measuring part dipped into fluid sample
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0011—Sample conditioning
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/85—Investigating moving fluids or granular solids
    • G01N2021/8578—Gaseous flow
    • G01N2021/8585—Gaseous flow using porous sheets, e.g. for separating aerosols

Definitions

  • the present invention relates to a novel device for measurement of the gas partial pressure in liquid media.
  • This process causes a change in the pH value in the electrolytic solution pH probe is measured.
  • the disadvantage of this measuring principle is that The fact that carbon dioxide is not direct, but its ionic form is measured. Since the proportion of the ionic form is less than 0.1% this method is not sufficiently precise. Apart from that, others bother volatile acidic or basic gases the pH value measurement. Furthermore very high maintenance is required.
  • pCO 2 optodes are known from the prior art. This is also a membrane-covered sensor system (SPIE Vol. 798 Fiber Optic Sensors II (1987) pp. 249-252; Anal. Chim. Acta 160 (1984) pp. 305-309; Proc. Int. Meeting on Chemical Sensors , Fukuoka, Japan, Elsevier, pp. 609-619, 1983, Talanta 35 (1988) 2 p.109-112, Anal.Chem. 65 (1993) p.331-337, Fresenius Z. Anal.Chem. 325 ( 1986) pp. 387-392).
  • pH indicators which change their absorption or fluorescence properties as a function of the proton concentration are used as the indicator phase (Anal. Chem. 52 (1980), pp. 864-869, DE-OS 3 343 636 and 3 343 637, U.S. Pat. Appl. 855,384).
  • gases for example carbon dioxide
  • Such carbon dioxide optodes work analogously to the Severinghaus electrodes.
  • the disadvantages of optical pH and thus pCO 2 measurements lie in the very limited analytical measuring range and the ionic strength dependency. The wide use of the optodes is also opposed by the disadvantages already mentioned with regard to the Severinghaus electrodes.
  • a sapphire ATR (attenuated total reflection) crystal is arranged in a flow measuring cell for fluid substances, for example beer, perpendicular to the direction of flow.
  • the infrared light which is fed to the crystal on one side, passes through the crystal and is totally reflected several times. With each reflection, the radiation gets several ⁇ m into the sample liquid and is weakened by the carbon dioxide present. The amount of residual light at the other end of the crystal is measured.
  • the disadvantage of this method is that no partial pressures can be measured. On the other hand, with changing fluids, the results can be falsified by changing the reflective properties.
  • German patent application 2435493 is a Differential pressure meter for the determination of carbonic acid known.
  • this device can only be used in flowing media. Therefore, it is particularly unsuitable for use in conventional stirred or solid medium reactors, such as those in particular in the fermentation industry.
  • German patent application 2926138 is a device for continuous measurement of the dissolved carbon dioxide content in Known liquids.
  • the measuring principle is based on the determination of the Conductivity difference.
  • the device is equipped with a membrane that on one side of the liquid containing dissolved carbon dioxide, and on the other hand from a neutral or basic Measuring fluid is flown.
  • One conductivity sensor each is in the path of the measuring liquid before and after the permeable Membrane arranged. Disadvantage of the measurement is that it is not for one changing in their chemical and physical properties Liquids is suitable.
  • a division into two beam paths is already from GB 2194333 known. With this method, only one light beam is passed through the material to be measured directed. The remaining radiation is used as a reference light also increase the accuracy.
  • the present invention has now set itself the task of a Device for measuring the partial pressure of dissolved in liquids To provide gases using optical methods that are not more the described disadvantages of the prior art Known devices and in particular the Gas partial pressure measurement with longer long-term stability of the device precise and changing chemical-physical in media Composition as well as in clear, cloudy and changeable cloudy Allows media.
  • measuring chamber e.g. in fermentations
  • Beverage production or wastewater treatment is used designed as a sterilizable device.
  • the membrane materials that have proven themselves in this area primarily for use. This includes above all polytetrafluoroethylene (silicone and other fluoride polymers).
  • gas selective membrane solubility membrane These can be used into the sample chamber (10) an equilibrium between the sample liquid and adjust the inner mixture.
  • the measuring chamber is preferably chemical and filled with biologically inert fluid. This is chosen so that it the gas to be determined, which through the membrane into the measuring chamber diffuses, absorbs. Suitable for this purpose are in the same way Liquids or gases can be used. The type of fluids mentioned judges the gases to be measured.
  • the preferred light emission source is Luminescent diodes used.
  • Luminescent diodes used.
  • the emission is relatively narrow-band, i.e. the use of Interference filtering is not essential to the appropriate To selectively determine gas. Due to the relatively low power consumption in principle it is possible to make the measurement setup portable with battery operation shape.
  • a decisive advantage over conventional infrared sources is the high level of performance. Therefore, it may be possible, without a comparison route or compensation circuits without building moving parts. Such a system is mechanically little susceptible. At the same time, the high level of performance guarantees a long service life Operation without recalibration.
  • the LEDs are so small dimensioned that a coupling of the light into optical fibers is easily possible. This allows the sensitive parts to be positioned externally are and are not one of the thermal-mechanical loads Subject to steam sterilization.
  • the luminescent diodes come compatible detectors.
  • photo diodes photo resistors and lead selenide photo detectors (PbSe) detectors.
  • PbSe lead selenide photo detectors
  • the latter mainly work in the infrared range and are particularly suitable for the determination of carbon dioxide.
  • optical fibers For guiding the light waves from the light emission source to the measuring chamber optical fibers are used. The same applies to the management of the Light from the measuring chamber to the measuring arrangement for determining the not absorbed light components.
  • the measuring arrangement is according to the invention preferably with a special circuit for evaluation, Storage and display of the signals connected. Because of that it is suitable the device according to the invention in particular for Automation of plants. Using an integrated Evaluation unit can automatically collect and all data be fed into a control process.
  • the possibility of a pressure-resistant is also advantageous according to the invention Design of the device. It is only necessary that Adapt the housing construction of the probe accordingly. In this manner can the device according to the invention at pressures of 200 bar be used. Preferably the probe is at pressures up to 20 bar used. When used for fermentation processes is only make sure that the probe is under sterilization conditions to withstand the increased pressures that occur.
  • Another object of the present invention is a method for Measurement of the partial pressure of gases dissolved in liquids.
  • This method is the device according to the invention in the Liquid present in the sample chamber is immersed in such a way that the membrane is completely wetted with sample liquid.
  • the gas to be determined selectively through the membrane into the measuring chamber diffuse.
  • Through the light emission source is over optical fiber a beam of light is passed through the measuring chamber. That over there diffusing gas absorbs part of the radiation.
  • the not absorbed Part of the light beam is through an optical fiber Measuring arrangement for determining the gas partial pressure supplied.
  • storage and display facilities can be measured from the non-absorbed Determine and evaluate the light beam the gas partial pressure.
  • one is preferably provided by luminescent diodes generated electromagnetic radiation used. Most notably the infrared range is preferred.
  • the device according to the invention and the method according to the invention are particularly suitable for using the measurement of the Carbon dioxide partial pressure.
  • Carbon dioxide represents a considerable amount Production factor in the food industry, especially in the Beverage industry. In the drinks themselves there is carbon dioxide for the Shelf life and the refreshing taste responsible. Most Today determinations are made via simultaneous printing and Temperature control.
  • a carbon dioxide partial pressure measurement is also required for optimal process control of biotechnical processes.
  • the supply of gases to the microorganisms and their inhibitory properties are a function of the corresponding partial pressures and not of the concentrations.
  • the carbon dioxide partial pressure has not been sufficiently taken into account to date.
  • a satisfactory solution to its determination has not yet been found.
  • the main problems when choosing a suitable determination method are the lack of equipment and the high chemical stability of carbon dioxide. Carbon dioxide is the highest oxidation state of carbon and is therefore very inert at room temperature. In solution, unlike other heterogeneous gases, it does not form hydrogen bonds.
  • the Measuring chamber filled with a carrier fluid for carbon dioxide.
  • This fluid must have solubility for carbon dioxide.
  • Another condition is that it is chemically and biologically inert.
  • the device is not specific Carrier fluid set. Their composition and chemical Rather, they depend on the type of gas to be measured and the conditions of use of the probe.
  • the device according to the invention then consists of the Probe (1).
  • the probe body is made of made of stainless steel. However, it is possible to manufacture from any other material. As a rule, it acts However, these are corrosion-free substances.
  • the probe (1) has a connector (2), which allows the Pressure-proof probe (1) in the pipeline or the wall (5) of a vessel use.
  • the connector (2) and the O-ring arrangement (3) allow the probe (1) to be sealed in an access pipe (4) on the Attach the wall (5).
  • the access pipe (4) has the corresponding Connection piece to the connection piece (2).
  • This construction enables the probe head undergo steam sterilization and use in sterile operation.
  • the Light source (6) around a luminescent diode and in the measuring arrangement (7) a photo receiver. Both parts of the device are with the electrical Provide lines (8) and (9).
  • the LED (6) is on the Line (8) supplied with power.
  • the photo receiver (7) transmits one Signal pulse via line (9) to a means for amplifying and Record the signal.
  • the luminescent diode (6) and the photo receiver (7) are outside the Liquid space (10) arranged. They are extrinsic Optical waveguides (12) and (13) which are used to transmit the light (12) from the liminescent diode (6) and the non-absorbed light to Serve photo receiver (7) used.
  • the optical fibers can be made any materials suitable for the transmission of light his. In the example according to the invention is in the infrared range worked. Therefore, there are preferably light guides made of transparent Material, e.g. from silver halides and chalcogenides.
  • optical fibers are thermally resilient and are therefore suitable for use in a steam-sterilizable environment.
  • the measuring chamber (14) is located at the tip of the head of the probe (1).
  • this is chemically and biologically inert fluid filled which is a high physical Has absorption capacity for carbon dioxide. In Fermentation processes select fluids whose boiling point is chosen so that it does not get too high during sterilization Pressure fluctuations comes.
  • the measuring space (14) is gas-permeable from the sample space (10) Separated membrane (11).
  • the membrane (11) is in the invention
  • Example a thermally stable membrane made of steam sterilizable Material is made.
  • polytetrafluoroethylene is used for this and / or silicone preferred.
  • the dissolved gas diffuses through the membrane (11) into the sample space (10) until equilibrium is reached. Because the diffusion of Gases controlled by a partial pressure membrane determines the Probe (1) the partial pressure. So the probe measures you biologically significant parameter; because the supply of the microorganisms is like all transport processes from the cells or into the cells, partial pressure and not concentration controlled.
  • the luminescent diode (6) emits narrowband light that is selective is absorbed by the gas to be determined.
  • the wavelength can be in with regard to the gas to be examined in both UV / VIS and in Infrared range. For carbon dioxide this is preferably 4.3 ⁇ m.
  • the emitted wavelength range can be limited by one Heat radiator with interference filter or preferably through a narrow band luminescent diode.
  • the particular advantage in use the luminescence diode is that the radiation can be modulated what detection is increased and effects such as DC drift are minimized.
  • the emitted radiation is the via the optical waveguide (12) Measuring room fed.
  • the gas present specifically weakens it emitted radiation.
  • the weakened light is partly from the Optical waveguide (13) recorded and the photo receiver (7) fed. This measures the weakened light and produces electrical signal proportional to the attenuated light. If modulated light is used, the electrical signal also modulate.
  • the length of the measuring chamber (14) corresponds to the optical path length.
  • a optimal optical path length is selected in the measuring room (14) so that the Probe (1) covers the entire measuring range.
  • the measuring range is inversely proportional to the path length. The smaller the path length of the Measuring chamber (14) of the probe (1), the larger the detectable Area and the smaller the resolution.
  • the advantages achieved by the invention are in particular that especially in the case of carbon dioxide partial pressure measurement by separation of the measuring room from the sample room not by the presence of clouding and changing their concentration arise. Furthermore, through the implementation of the membrane Measurement of partial pressure guaranteed. In principle it is possible to use Using Henry's law to convert concentration into partial pressures. But it requires the simultaneous knowledge of temperature and Pressure as well as the media properties. The latter is particularly the case with Difficult to use fermentation media. Furthermore, the Long-term stability, accuracy and the measuring range compared to pH-sensitive Partial pressure probes increased.
  • the probe according to the invention is both in the beverage industry Can also be used particularly well in biotechnology.
  • probes for measuring ranges from to to create 10 bar.

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Abstract

The present invention concerns a device for measuring the partial pressure of gases dissolved in liquids. The device comprises (a) a measurement chamber (14) which is separated by a gas-permeable membrane (11) permeable to the dissolved gas from a sample chamber (10) containing the liquid with the dissolved gas; (b) a light emission source (6) for producing a light beam which passes through the measurement chamber (14) and is of a wavelength absorbed by the dissolved gas; (c) a measurement device (7) for determining the intensity of the light beam leaving the measurement chamber.

Description

Die vorliegende Erfindung betrifft eine neuartige Vorrichtung zur Messung des Gaspartialdrucks in flüssigen Medien.The present invention relates to a novel device for measurement of the gas partial pressure in liquid media.

Vor allem im Bereich der Fermentationstechnologie hat sich zunehmend die Notwendigkeit ergeben, die Messung von Gasen über die Bestimmung des Partialdruckes vorzunehmen. So sind für die Ermittlung des Sauerstoff- und des Kohlendioxid-Partialdruckes spezielle Sonden entwickelt worden. Ein weitverbreitetes Beispiel hierfür sind die sog. Severinghauselektroden. Diese Vorrichtungen arbeiten mit membranbedeckten Einstab-pH-Elektroden (DE-OS 25 08 637, Biotechnol. Bioeng. 22(1980), 2411-2416, Biotechnol. Bioeng. 23(1981), 461-466). Bei diesem System befindet sich zwischen der gasselektiven Membran und der pH-Elektrode eine Elektrolytlösung oder -paste. Das Meßprinzip beruht darauf, daß Kohlendioxid in wäßriger Lösung Kohlensäure bildet, die zu einem Bicarbonatanion und einem Proton dissoziiert. Dieser Vorgang bewirkt in der Elektrolytlösung eine pH-Werts-Änderung, die mittels der pH-Sonde gemessen wird. Der Nachteil dieses Meßprinzips ist die Tatsache, daß Kohlendioxid nicht direkt, sondern seine ionische Form gemessen wird. Da der Anteil der ionischen Form unter 0,1 % liegt, ist diese Methode nicht ausreichend genau. Abgesehen davon stören andere flüchtige saure oder basische Gase die pH-Werts-Messung. Des weiteren ist ein sehr hoher Wartungsaufwand erforderlich.Especially in the field of fermentation technology has been increasing the need to measure the measurement of gases of the partial pressure. So for the determination of the Special probes for oxygen and carbon dioxide partial pressure has been developed. A common example of this are the so-called Severinghauselektroden. These devices work with membrane-covered Single-rod pH electrodes (DE-OS 25 08 637, Biotechnol. Bioeng. 22: 2411-2416 (1980), Biotechnol. Bioeng. 23: 461-466 (1981). at this system is located between the gas selective membrane and an electrolyte solution or paste in the pH electrode. The measuring principle is based insist that carbon dioxide forms carbonic acid in aqueous solution, the dissociated into a bicarbonate anion and a proton. This process causes a change in the pH value in the electrolytic solution pH probe is measured. The disadvantage of this measuring principle is that The fact that carbon dioxide is not direct, but its ionic form is measured. Since the proportion of the ionic form is less than 0.1% this method is not sufficiently precise. Apart from that, others bother volatile acidic or basic gases the pH value measurement. Furthermore very high maintenance is required.

Ferner sind aus dem Stand der Technik pCO2-Optoden bekannt. Auch hier handelt es sich um ein membranbedecktes Sensorsystem (SPIE Vol. 798 Fiber Optic Sensors II (1987) S. 249-252; Anal. Chim. Acta 160 (1984) S. 305-309; Proc. Int. Meeting on Chemical Sensors, Fukuoka, Japan, Elsevier, S. 609-619, 1983, Talanta 35(1988)2 S.109-112, Anal.Chem. 65(1993) S.331-337, Fresenius Z. Anal. Chem. 325(1986) S. 387-392). Bei den pH-Optoden werden pH-Indikatoren, die in Abhängigkeit von der Protonenkonzentration ihre Absorptions- oder Fluoreszenzeigenschaften ändern, als Indikatorphase verwendet (Anal.Chem. 52(1980) S.864-869, DE-OS 3 343 636 und 3 343 637, US-Pat. Appl. 855 384). Trennt man den Indikator mit einer gaspermeablen Membran von dem Meßgut ab, können nur Gase, beispielsweise Kohlendioxid, durch die Membran zur Indikatorphase dringen und dort eine pH-Werts-Änderung durch Hydrolyse verursachen. Solche Kohlendioxid-Optoden arbeiten analog zu den Severinghaus-Elektroden. Die Nachteile optischer pH- und damit pCO2-Messungen liegen in dem sehr eingeschränkten analytischen Meßbereich und der lonenstärkeabhängigkeit. Einer breiten Anwendung der Optoden stehen daneben die bereits hinsichtlich der Severinghaus-Elektroden genannten Nachteile entgegen.Furthermore, pCO 2 optodes are known from the prior art. This is also a membrane-covered sensor system (SPIE Vol. 798 Fiber Optic Sensors II (1987) pp. 249-252; Anal. Chim. Acta 160 (1984) pp. 305-309; Proc. Int. Meeting on Chemical Sensors , Fukuoka, Japan, Elsevier, pp. 609-619, 1983, Talanta 35 (1988) 2 p.109-112, Anal.Chem. 65 (1993) p.331-337, Fresenius Z. Anal.Chem. 325 ( 1986) pp. 387-392). In the case of the pH optodes, pH indicators which change their absorption or fluorescence properties as a function of the proton concentration are used as the indicator phase (Anal. Chem. 52 (1980), pp. 864-869, DE-OS 3 343 636 and 3 343 637, U.S. Pat. Appl. 855,384). If the indicator is separated from the material to be measured with a gas-permeable membrane, only gases, for example carbon dioxide, can penetrate through the membrane to the indicator phase and cause a change in pH value there by hydrolysis. Such carbon dioxide optodes work analogously to the Severinghaus electrodes. The disadvantages of optical pH and thus pCO 2 measurements lie in the very limited analytical measuring range and the ionic strength dependency. The wide use of the optodes is also opposed by the disadvantages already mentioned with regard to the Severinghaus electrodes.

Es ist ferner bekannt, die CO2-Konzentration in Flüssigkeiten mittels abgeschwächter Totalreflektion zu bestimmen (The Chemical Engineer 498 (1991) S. 18). In einer Durchflußmeßze'le für fluide Stoffe, beispielsweise Bier, ist senkrecht zur Strömungsrichtung ein Sapphir-ATR (Attenuated Total Reflectance)-Kristall angeordnet. Das Infrarotlicht, das an einer Seite dem Kristall zugeführt wird, durchläuft den Kristall und wird mehrmals total reflektiert. Bei jeder Reflektion gelangt die Strahlung mehrere um in die Probenflüssigkeit und wird durch vorhandenes Kohlendioxid abgeschwächt. Die Restlichtmenge am anderen Ende des Kristalls wird gemessen. Nachteil dieser Methode ist, daß keine Partialdrücke gemessen werden können. Andererseits können bei sich verändernden Fluiden durch die Änderung der Reflektionseigenschaften Verfälschungen der Ergebnisse auftreten.It is also known to determine the CO 2 concentration in liquids by means of attenuated total reflection (The Chemical Engineer 498 (1991) p. 18). A sapphire ATR (attenuated total reflection) crystal is arranged in a flow measuring cell for fluid substances, for example beer, perpendicular to the direction of flow. The infrared light, which is fed to the crystal on one side, passes through the crystal and is totally reflected several times. With each reflection, the radiation gets several µm into the sample liquid and is weakened by the carbon dioxide present. The amount of residual light at the other end of the crystal is measured. The disadvantage of this method is that no partial pressures can be measured. On the other hand, with changing fluids, the results can be falsified by changing the reflective properties.

Aus der deutschen Offenlegungsschrift 2435493 ist ein Differenzdruckmeßgerät für die Bestimmung von Kohlensäure bekannt. Dieses Gerät kann jedoch nur in strömenden Medien eingesetzt werden. Daher eignet es sich insbesondere nicht für die Verwendung in herkömmlichen Rühr- oder Festmittelreaktoren, wie sie insbesondere in der Fermentationsindustrie zum Einsatz kommen.From the German patent application 2435493 is a Differential pressure meter for the determination of carbonic acid known. However, this device can only be used in flowing media. Therefore, it is particularly unsuitable for use in conventional stirred or solid medium reactors, such as those in particular in the fermentation industry.

Aus der deutschen Offenlegungsschrift 2926138 ist eine Einrichtung zur kontinuierlichen Messung des Gehaltes an gelöstem Kohlendioxid in Flüssigkeiten bekannt. Das Meßprinzip beruht auf der Bestimmung der Leitfähigkeitdifferenz. Das Gerät ist mit einer Membram ausgestattet, die auf einer Seite von der gelöstes Kohlendioxid enthaltenden Flüssigkeit, und auf der anderen Seite von einer neutralen oder basischen Meßflüssigkeit angeströmt wird. Je ein Leitfähigkeits-Meßwertaufnehmer ist im Leitungsweg der Meßflüssigkeit vor und nach der permeablen Membran angeordnet. Nachteil der Messung ist, daß sie nicht für eine sich in ihren chemischen und physikalischen Eigenschaften ändernden Flüssigkeiten geeignet ist.From the German patent application 2926138 is a device for continuous measurement of the dissolved carbon dioxide content in Known liquids. The measuring principle is based on the determination of the Conductivity difference. The device is equipped with a membrane that on one side of the liquid containing dissolved carbon dioxide, and on the other hand from a neutral or basic Measuring fluid is flown. One conductivity sensor each is in the path of the measuring liquid before and after the permeable Membrane arranged. Disadvantage of the measurement is that it is not for one changing in their chemical and physical properties Liquids is suitable.

Aus der europäischen Patentanmeldung 0462755 ist es ferner bekannt, Gase, beispielsweise CO2 durch Infrarot-Absorptionsmessung zu bestimmen. Hierbei wird der Infrarotlichtstrahl durch das zu messende Fluid geschickt. Der Lichtstrahl wird in zwei oder mehr Komponenten geteilt. Diese geteilten Lichtstrahlen werden sodann gemessen. Nachteil dieser Meßanordnung ist, daß sie nicht die Ermittlung von Partialdrücken erlaubt und empfindlich gegenüber streuenden Partikeln der Probenflüssigkeit ist.From European patent application 0462755 it is also known to determine gases, for example CO 2, by infrared absorption measurement. The infrared light beam is sent through the fluid to be measured. The light beam is divided into two or more components. These split light beams are then measured. The disadvantage of this measuring arrangement is that it does not allow the determination of partial pressures and is sensitive to scattering particles in the sample liquid.

Eine Aufteilung in zwei Strahlengängen ist bereits aus der GB 2194333 bekannt. Bei diesem Verfahren wird nur ein Lichtstrahl durch das Meßgut geleitet. Die restliche Strahlung wird als Referenzlicht genutzt, um ebenfalls die Genauigkeit zu erhöhen.A division into two beam paths is already from GB 2194333 known. With this method, only one light beam is passed through the material to be measured directed. The remaining radiation is used as a reference light also increase the accuracy.

In einer weiteren Veröffentlichung ist ein sog. gechopptes Gasanalysegerät beschrieben, welches ebenfalls mit Lumineszenzdioden arbeitet (Laser und Optoelektronik 17(1985)3, S. 308-310, Wiegleb, G.: Einsatz von LED-Strahlungsquellen in Analysengeräten).In another publication is a so-called chopped Gas analyzer described, which also with luminescent diodes works (laser and optoelectronics 17 (1985) 3, pp. 308-310, Wiegleb, G .: Use of LED radiation sources in analysis devices).

Diesen Geräten und Verfahren ist gemeinsam, daß sie nur Konzentrationen bestimmen. Das Meßgut wird direkt in den Strahlengang gegeben und gemessen. Dies ist möglich für Gase und Flüssigkeiten ohne streuende Partikel mit medienkonstanter Zusammensetzung, in denen Störungen durch einen Blindwert erfaßt werden können. Mit den beschriebenen optischen Methoden lassen sich jedoch nicht Partialdrücke bestimmen. Ebensowenig ist ein Einsatz für medienveränderliche Zusammensetzung und trübende Partikel enthaltende Flüssigkeiten möglich.These devices and methods have in common that they only Determine concentrations. The material to be measured is directly in the beam path given and measured. This is possible for gases and liquids without scattering particles with constant composition, in which disturbances can be detected by a blank value. With the However, optical methods described cannot be partial pressures determine. Nor is there any use for media-changeable Liquids containing composition and opacifying particles possible.

Die vorliegende Erfindung hat sich nunmehr die Aufgabe gestellt, eine Vorrichtung zur Messung des Partialdruckes von in Flüssigkeiten gelösten Gasen mittels optischer Methoden zur Verfügung zu stellen, die nicht mehr die geschilderten Nachteile der aus dem Stand der Technik bekannten Vorrichtungen aufweist und die insbesondere die Gaspartialdruckmessung bei längerer Langzeitstabilität der Vorrichtung präzise und in Medien sich ändernder chemisch-physikalischer Zusammensetzung sowie in klaren, trüben und veränderlich trüben Medien zuläßt.The present invention has now set itself the task of a Device for measuring the partial pressure of dissolved in liquids To provide gases using optical methods that are not more the described disadvantages of the prior art Known devices and in particular the Gas partial pressure measurement with longer long-term stability of the device precise and changing chemical-physical in media Composition as well as in clear, cloudy and changeable cloudy Allows media.

Diese Aufgabe wird dadurch gelöst, daß die Vorrichtung

  • a) aus einer Meßkammer, die mittels einer gaspermeablen Membrane, die für das zu bestimmende Gas permeabel ist, von einem Probenraum, der die Flüssigkeit mit dem darin gelösten, zu bestimmenden Gas enthält, abgetrennt ist,
  • b) einer Lichtemissionsquelle zur Erzeugung eines durch die Meßkammer hindurchtretenden Lichtstrahls mit einer Wellenlänge, die durch das zu bestimmende Gas absorbiert wird, und
  • c) einer Meßanordnung zur Bestimmung des die Meßkammer verlassenden Lichtstrahls besteht, und
  • d) die Meßkammer mit einem chemisch und biologisch inerten Fluid zur Absorption des in bestimmenden Gases gefüllt ist.
    • This object is achieved in that the device
  • a) from a measuring chamber which is separated by means of a gas-permeable membrane which is permeable to the gas to be determined from a sample space which contains the liquid with the gas to be determined dissolved therein,
  • b) a light emission source for generating a light beam which passes through the measuring chamber and has a wavelength which is absorbed by the gas to be determined, and
  • c) there is a measuring arrangement for determining the light beam leaving the measuring chamber, and
  • d) the measuring chamber is filled with a chemically and biologically inert fluid for the absorption of the gas in the determination.

    • Erfindungsgemäß sind Meßkammer, Lichtemissionsquelle und Meßanordnung in einer stabförmigen Sonde angeordnet. Sofern diese im Bereich der Biotechnologie, z.B. bei Fermentationen, Getränkeherstellungen oder Abwasserreinigungen zum Einsatz kommt, ist sie als sterilisierbare Vorrichtung ausgelegt. Da im Bereich der Fermentationstechnik vorwiegend mittels Dampf sterilisiert wird, sind die Sondenmaterialien auf diese Verhältnisse abzustimmen. Daher kommen die in diesem Bereich bewährten Membranmaterialien auch in erster Linie zum Einsatz. Hierzu zählt vor allem Polytetrafluorethylen (Silicon und andere fluoride Polymere). Bewährt haben sich erfindungsgemäß als gasselektive Membrane Löslichkeitsmembrane. Diese können bei Einsatz in den Probenraum (10) ein Gleichgewicht zwischen der Probenflüssigkeit und dem inneren Gemisch einstellen.According to the invention, measuring chamber, light emission source and Measuring arrangement arranged in a rod-shaped probe. If this in Area of biotechnology, e.g. in fermentations, Beverage production or wastewater treatment is used designed as a sterilizable device. Because in the field of fermentation technology are mainly sterilized by steam Adjust probe materials to these conditions. Hence come the membrane materials that have proven themselves in this area primarily for use. This includes above all polytetrafluoroethylene (silicone and other fluoride polymers). Have proven themselves according to the invention as gas selective membrane solubility membrane. These can be used into the sample chamber (10) an equilibrium between the sample liquid and adjust the inner mixture.

    Die Meßkammer ist erfindungsgemäß vorzugsweise mit einem chemisch und biologisch inerten Fluid gefüllt. Dieses wird so ausgewählt, daß es das zu bestimmende Gas, das durch die Membran in die Meßkammer diffundiert, absorbiert. Für diesen Zweck sind in gleicher Weise geeignete Flüssigkeiten oder Gase einsetzbar. Die Art der genannten Fluide richtet sich nach den zu messenden Gasen.According to the invention, the measuring chamber is preferably chemical and filled with biologically inert fluid. This is chosen so that it the gas to be determined, which through the membrane into the measuring chamber diffuses, absorbs. Suitable for this purpose are in the same way Liquids or gases can be used. The type of fluids mentioned judges the gases to be measured.

    Als Lichtemissionsquelle werden erfindungsgemäß vorzugsweise Lumineszenzdioden eingesetzt. Der Einsatz dieser Vorrichtungen hat folgende Vorteile:According to the invention, the preferred light emission source is Luminescent diodes used. The use of these devices has following advantages:

    Die Emission ist relativ schmalbandig, d.h. der Einsatz von Interferenzfiltern ist nicht unbedingt erforderlich, um das entsprechende Gas selektiv zu bestimmen. Durch den relativ niedrigen Stromverbrauch ist es prinzipiell möglich, den Meßaufbau tragbar mit Akkubetrieb zu gestalten. Ein entscheidender Vorteil gegenüber den herkömmlichen Infrarotquellen ist die hohe Leistungskonstanz. Daher ist es u.U. möglich, ohne Vergleichsstrecke auszukommen oder Kompensationsschaltungen ohne bewegte Teile aufzubauen. Solch ein System ist mechanisch wenig anfällig. Gleichzeitig garantiert die hohe Leistungskonstanz einen langen Betrieb ohne Nachkalibrierung. Die Lumineszenzdioden sind so klein dimensioniert, daß eine Einkopplung des Lichts in Lichtwellenleiter problemlos möglich ist. So können die sensitiven Teile extern positioniert werden und sind nicht den thermisch-mechanischen Belastungen einer Dampfsterilisation unterworfen. The emission is relatively narrow-band, i.e. the use of Interference filtering is not essential to the appropriate To selectively determine gas. Due to the relatively low power consumption in principle it is possible to make the measurement setup portable with battery operation shape. A decisive advantage over conventional infrared sources is the high level of performance. Therefore, it may be possible, without a comparison route or compensation circuits without building moving parts. Such a system is mechanically little susceptible. At the same time, the high level of performance guarantees a long service life Operation without recalibration. The LEDs are so small dimensioned that a coupling of the light into optical fibers is easily possible. This allows the sensitive parts to be positioned externally are and are not one of the thermal-mechanical loads Subject to steam sterilization.

    In dem erfindungsgemäßen Verfahren kann auch mit verschiedenen Wellenlängen, vorzugsweise zwei verschiedenen Wellenlängen, gearbeitet, um die Genauigkeit zu erhöhen. Die Verfahren zur Erhöhung der Meßgenauigkeit und Kompensation von Schwankungen in den elektronischen Bauteilen sind allgemein bekannt und veröffentlicht (Meas.Sci.Technol. 3(1992)2 191-195, Sean F. Johnston: Gas Monitors Employing Infrared LEDs).In the method according to the invention can also with various Wavelengths, preferably two different wavelengths, worked to increase accuracy. The procedure for raising the measuring accuracy and compensation of fluctuations in the electronic components are generally known and published (Meas.Sci.Technol. 3 (1992) 2 191-195, Sean F. Johnston: Gas Monitors Employing Infrared LEDs).

    Ferner kommen erfindungsgemäß die zu den Lumineszenzdioden kompatiblen Detektoren zum Einsatz. Als solche eignen sich insbesondere Fotodioden, Fotowiderstände und Bleiselenidfotodetektoren (PbSe-Detektoren). Letztere arbeiten vorwiegend im infraroten Bereich und sind vor allem zur Bestimmung von Kohlendioxid geeignet.Furthermore, according to the invention, the luminescent diodes come compatible detectors. As such are suitable in particular photo diodes, photo resistors and lead selenide photo detectors (PbSe) detectors. The latter mainly work in the infrared range and are particularly suitable for the determination of carbon dioxide.

    Zur Leitung der Lichtwellen von der Lichtemissionsquelle zur Meßkammer werden Lichtwellenleiter eingesetzt. Gleiches gilt für die Leitung des Lichtes von der Meßkammer zur Meßanordnung für die Bestimmung der nicht absorbierten Lichtanteile. Die Meßanordnung ist erfindungsgemäß vorzugsweise mit einer speziellen Schaltung zur Auswertung, Speicherung und Anzeige der Signale verbunden. Aufgrunddessen eignet sich die erfindungsgemäße Vorrichtung insbesondere für die Automatisierung von Anlagen. Mittels einer integrierten Auswertungseinheit können automatisch sämtliche Daten erfaßt und einem Regelungsprozeß zugeführt werden.For guiding the light waves from the light emission source to the measuring chamber optical fibers are used. The same applies to the management of the Light from the measuring chamber to the measuring arrangement for determining the not absorbed light components. The measuring arrangement is according to the invention preferably with a special circuit for evaluation, Storage and display of the signals connected. Because of that it is suitable the device according to the invention in particular for Automation of plants. Using an integrated Evaluation unit can automatically collect and all data be fed into a control process.

    Erfindungsgemäß vorteilhaft ist auch die Möglichkeit einer druckfesten Ausgestaltung der Vorrichtung. Es ist lediglich notwendig, die Gehäusekonstruktion der Sonde entsprechend anzupassen. Auf diese Art kann die erfindungsgemäße Vorrichtung bei Drücken von 200 bar eingesetzt werden. Vorzugsweise wird die Sonde bei Drücken bis zu 20 bar verwendet. Bei dem Einsatz für Fermentationsprozesse ist lediglich darauf zu achten, daß die Sonde den unter Sterilisationsbedingungen auftretenden erhöhten Drücken standzuhalten hat.The possibility of a pressure-resistant is also advantageous according to the invention Design of the device. It is only necessary that Adapt the housing construction of the probe accordingly. In this manner can the device according to the invention at pressures of 200 bar be used. Preferably the probe is at pressures up to 20 bar used. When used for fermentation processes is only make sure that the probe is under sterilization conditions to withstand the increased pressures that occur.

    Weiterer Gegenstand der vorliegenden Erfindung ist ein Verfahren zur Messung des Partialdruckes von in Flüssigkeiten gelösten Gasen. Bei diesem Verfahren wird die erfindungsgemäße Vorrichtung in die in dem Probenraum vorhandene Flüssigkeit derart eingetaucht, daß die Membran vollständig mit Probenflüssigkeit benetzt ist. Infolgedessen kann nunmehr das zu bestimmende Gas selektiv durch die Membran in die Messkammer diffundieren. Durch die Lichtemissionsquelle wird über Lichtwellenleiter ein Lichtstrahl durch die Meßkammer geleitet. Das dort dorthin diffundierende Gas absorbiert einen Teil der Strahlung. Der nicht absorbierte Teil des Lichtstrahls wird über einen Lichtwellenleiter der Meßanordnung für die Bestimmung des Gaspartialdruckes zugeleitet. Durch entsprechende Auswertungs-, Speicherungs- und Anzeigeeinrichtungen läßt sich anhand der Messung des nicht absorbierten Lichtstrahls der Gaspartialdruck bestimmen und auswerten.Another object of the present invention is a method for Measurement of the partial pressure of gases dissolved in liquids. at This method is the device according to the invention in the Liquid present in the sample chamber is immersed in such a way that the membrane is completely wetted with sample liquid. As a result, now the gas to be determined selectively through the membrane into the measuring chamber diffuse. Through the light emission source is over optical fiber a beam of light is passed through the measuring chamber. That over there diffusing gas absorbs part of the radiation. The not absorbed Part of the light beam is through an optical fiber Measuring arrangement for determining the gas partial pressure supplied. Through appropriate evaluation, storage and display facilities can be measured from the non-absorbed Determine and evaluate the light beam the gas partial pressure.

    Erfindungsgemäß wird vorzugsweise eine durch Lumineszenzdioden erzeugte elektromagnetische Strahlung eingesetzt. Ganz besonders bevorzugt wird der infrarote Bereich.According to the invention, one is preferably provided by luminescent diodes generated electromagnetic radiation used. Most notably the infrared range is preferred.

    Die erfindungsgemäße Vorrichtung und das erfindungsgemäße Verfahren eignen sich insbesondere zum Einsatz der Messung des Kohlendioxidpartialdrucks. Kohlendioxid stellt einen beträchtlichen Produktionsfaktor in der Lebensmittelindustrie, insbesondere in der Getränkeindustrie dar. In den Getränken selbst ist Kohlendioxid für die Haltbarkeit und den erfrischenden Geschmack verantwortlich. Die meisten Bestimmungen erfolgen heute über gleichzeitige Druck- und Temperaturkontrolle.The device according to the invention and the method according to the invention are particularly suitable for using the measurement of the Carbon dioxide partial pressure. Carbon dioxide represents a considerable amount Production factor in the food industry, especially in the Beverage industry. In the drinks themselves there is carbon dioxide for the Shelf life and the refreshing taste responsible. Most Today determinations are made via simultaneous printing and Temperature control.

    Für eine optimale Prozeßführung biotechnischer Prozesse ist ebenfalls auch eine Kohlendioxidpartialdruckmessung erfordertich. Von Bedeutung in diesem Zusammenhang ist die Tatsache, daß die Versorgung der Mikroorganismen mit Gasen und deren inhibitorischen Eigenschaften eine Funktion der entsprechenden Partialdrücke und nicht der Konzentrationen sind. Trotz dieser Kenntnis wird der Kohlendioxidpartialdruck bis heute nicht hinreichend berücksichtigt. Eine befriedigende Lösung zu seiner Bestimmung ist noch nicht gefunden. Die Hauptprobleme bei der Wahl einer geeigneten Bestimmungsmethode sind fehlende apparative Möglichkeiten und die hohe chemische Stabilität des Kohlendioxids. Kohlendioxid stellt die höchste Oxidationsstufe von Kohlenstoff dar und ist bei Raumtemperatur daher sehr reaktionsträge. In gelöster Form bildet es im Gegensatz zu anderen heterogenen Gasen keine Wasserstoffbrückenbindungen aus. Bei einer Dissoziationskonstante für Kohlensäure von 2x10-4M liegt nur ein sehr geringer Teil in Form gelöster lonen vor. Eine Meßsonde, die auf der Bestimmung der ionischen Form beruht, ist deshalb schon mit einem Fehler behaftet. Für eine genaue Methode ist es daher erforderlich, direkt das gelöste Kohlendioxid zu bestimmen. Für eine Messung bei Raumtemperaturen steht die Absorptionsmessung von Kohlendioxid zur Verfügung. Die Absorptionsmessung im infratoten Bereich ist mit den vorhandenen Abgasanalysenapparaten Stand der Technik. Die Bestimmung aus der Abluft liefert jedoch Konzentrationen und keine Partialdrücke. Mit Hilfe des Henry'schen Gesetzes lassen sich Konzentrationen in Partialdrücke umrechnen und umgekehrt. Die Umrechnung von Konzentationen in Partialdrücken gestaltet sich für Kohlendioxid im Gegensatz zu Sauerstoff schwieriger, da die Henry-Konstante durch den pH-Wert und Medienbestandteile beeinflußt wird. Fluktuationen des pH-Wertes führen zu zeitlichen Veränderungen der Kohlendioxidkonzentration in der Abluft. Besonders bei basischen Fermentationen und in großen Reaktoren führt die Kohlendioxidspeicherung der Medien zu zeitlichem Überschwingen des Meßsignals bei Annäherung an ein neues Gleichgewicht. Solche Signale können als Änderung des Metabolismus fehlinterpretiert werden.A carbon dioxide partial pressure measurement is also required for optimal process control of biotechnical processes. Of importance in this context is the fact that the supply of gases to the microorganisms and their inhibitory properties are a function of the corresponding partial pressures and not of the concentrations. Despite this knowledge, the carbon dioxide partial pressure has not been sufficiently taken into account to date. A satisfactory solution to its determination has not yet been found. The main problems when choosing a suitable determination method are the lack of equipment and the high chemical stability of carbon dioxide. Carbon dioxide is the highest oxidation state of carbon and is therefore very inert at room temperature. In solution, unlike other heterogeneous gases, it does not form hydrogen bonds. With a dissociation constant for carbonic acid of 2x10 -4 M, only a very small part is in the form of dissolved ions. A measuring probe which is based on the determination of the ionic form is therefore already subject to an error. For an exact method, it is therefore necessary to determine the dissolved carbon dioxide directly. The absorption measurement of carbon dioxide is available for a measurement at room temperature. Absorption measurement in the infrared range is state of the art with the existing exhaust gas analyzers. However, the determination from the exhaust air provides concentrations and no partial pressures. With the help of Henry's law, concentrations can be converted into partial pressures and vice versa. The conversion of concentrations into partial pressures is more difficult for carbon dioxide than for oxygen, since the Henry constant is influenced by the pH value and media components. Fluctuations in the pH value lead to changes in the carbon dioxide concentration in the exhaust air over time. Particularly in basic fermentations and in large reactors, the carbon dioxide storage of the media leads to the measurement signal overshooting when a new equilibrium is approached. Such signals can be misinterpreted as a change in metabolism.

    Durch den Einsatz der erfindungsgemäßen Vorrichtung werden insbesondere die aufgezeigten Probleme der Kohlendioxidpartialdruckmessung gelöst. In diesem Falle wird die Meßkammer mit einem Trägerfluid für Kohlendioxid gefüllt. Dieses Fluid muß eine Löslichkeit für Kohlendioxid aufweisen. Weitere Bedingung ist, daß sie chemisch und biologisch inert ist. Für eine Dampfsterilisation ist weiterhin von Vorteil, wenn das Fluid einen höheren Siedepunkt als das Meßgut besitzt, um Druckschwankungen weitgehend zu vermeiden. Erfindungsgemäß ist die Vorrichtung jedoch nicht auf eine bestimmte Trägerflüssigkeit festgelegt. Deren Zusammensetzung und chemische Natur richten sich vielmehr nach der Art des zu messenden Gases und den Einsatzbedingungen der Sonde.By using the device according to the invention in particular the problems of the Carbon dioxide partial pressure measurement solved. In this case the Measuring chamber filled with a carrier fluid for carbon dioxide. This fluid must have solubility for carbon dioxide. Another condition is that it is chemically and biologically inert. For steam sterilization still beneficial if the fluid has a higher boiling point than that Has material to be measured in order to largely avoid pressure fluctuations. According to the invention, however, the device is not specific Carrier fluid set. Their composition and chemical Rather, they depend on the type of gas to be measured and the conditions of use of the probe.

    Im folgenden wird die Erfindung unter Bezugnahme auf die Figur näher beschrieben. Die erfindungsgemäße Vorrichtung besteht danach aus der Sonde (1). Der Sondenkörper ist im erfindungsgemäßen Beispiel aus rostfreiem Stahl hergestellt. Es ist jedoch möglich, eine Herstellung aus jedem anderen beliebigen Material vorzunehmen. In der Regel handelt es sich hierbei jedoch um korrosionsfreie Stoffe. In the following the invention with reference to the figure described. The device according to the invention then consists of the Probe (1). In the example according to the invention, the probe body is made of made of stainless steel. However, it is possible to manufacture from any other material. As a rule, it acts However, these are corrosion-free substances.

    Die Sonde (1) weist ein Anschlußstück (2) auf, welches es erlaubt, die Sonde (1) in die Rohrleitung oder die Wand (5) eines Gefäßes druckfest einzusetzen. Das Anschlußstück (2) und die O-Ring-Anordnung (3) erlauben es, die Sonde (1) abdichtend in einem Zugangsrohr (4) an der Wand (5) zu befestigen. Das Zugangsrohr (4) weist das entsprechende Anschlußstück zum Anschlußstück (2) auf.The probe (1) has a connector (2), which allows the Pressure-proof probe (1) in the pipeline or the wall (5) of a vessel use. The connector (2) and the O-ring arrangement (3) allow the probe (1) to be sealed in an access pipe (4) on the Attach the wall (5). The access pipe (4) has the corresponding Connection piece to the connection piece (2).

    Durch diesen Aufbau wird die Möglichkeit gegeben, den Sondenkopf einer Dampfsterilisation zu unterziehen und im Sterilbetrieb zu nutzen.This construction enables the probe head undergo steam sterilization and use in sterile operation.

    Innerhalb der Sonde (1) sind eine Lichtquelle (6) und eine Meßanordnung (7) vorhanden. Im erfindungsgemäßen Beispiel handelt es sich bei der Lichtquelle (6) um eine Lumineszenzdiode und bei der Meßanordnung (7) um einen Fotoempfänger. Beide Geräteteile sind mit den elektrischen Leitungen (8) und (9) versehen. Die Lumineszenzdiode (6) wird über die Leitung (8) mit Strom versorgt. Der Fotoempfänger (7) überträgt einen Signalimpuls über die Leitung (9) zu einem Mittel zum Verstärken und Aufzeichnen des Signals.Inside the probe (1) are a light source (6) and a measuring arrangement (7) available. In the example according to the invention, the Light source (6) around a luminescent diode and in the measuring arrangement (7) a photo receiver. Both parts of the device are with the electrical Provide lines (8) and (9). The LED (6) is on the Line (8) supplied with power. The photo receiver (7) transmits one Signal pulse via line (9) to a means for amplifying and Record the signal.

    Die Lumineszenzdiode (6) und der Fotoempfänger (7) sind außerhalb des Flüssigkeitsraums (10) angeordnet. Sie sind über die extrinsischen Lichtwellenleiter (12) und (13), welche zum Übertragen des Lichts (12) von der Limineszenzdiode (6) und des nicht absorbierten Lichts zum Fotoempfänger (7) dienen, eingesetzt. Die Lichtwellenleiter können aus beliebigen für die Übertragung von Licht geeigneten Materialien hergestellt sein. Im erfindungsgemäßen Beispiel wird im infraroten Bereich gearbeitet. Es kommen daher vorzugsweise Lichtleiter aus transparentem Material, z.B. aus Silberhalogeniden und Chalcogeniden in Betracht. The luminescent diode (6) and the photo receiver (7) are outside the Liquid space (10) arranged. They are extrinsic Optical waveguides (12) and (13) which are used to transmit the light (12) from the liminescent diode (6) and the non-absorbed light to Serve photo receiver (7) used. The optical fibers can be made any materials suitable for the transmission of light his. In the example according to the invention is in the infrared range worked. Therefore, there are preferably light guides made of transparent Material, e.g. from silver halides and chalcogenides.

    Diese Lichtwellenleiter sind thermisch belastbar und eignen sich somit für den Einsatz in dampfsterilisierbarer Umgebung.These optical fibers are thermally resilient and are therefore suitable for use in a steam-sterilizable environment.

    An der Spitze des Kopfes der Sonde (1) befindet sich der Meßraum (14). Dieser ist im erfindungsgemäßen Beispiel mit einem chemisch und biologisch inerten Fluid gefüllt, das ein hohes physikalisches Absorptionsvermögen für Kohlendioxid aufweist. In Fermentationsverfahren werden Fluide ausgewählt, deren Siedepunkt derart gewählt ist, daß es während der Sterilisation nicht zu Druckschwankungen kommt.The measuring chamber (14) is located at the tip of the head of the probe (1). In the example according to the invention, this is chemically and biologically inert fluid filled which is a high physical Has absorption capacity for carbon dioxide. In Fermentation processes select fluids whose boiling point is chosen so that it does not get too high during sterilization Pressure fluctuations comes.

    Der Meßraum (14) ist von dem Probenraum (10) über die gaspermeable Membran (11) getrennt. Die Membran (11) ist im erfindungsgemäßen Beispiel eine thermisch stabile Membran, die aus dampfsterilisierbarem Material gefertigt ist. Erfindungsgemäß wird hierfür Polytetrafluorethylen und/oder Silicon bevorzugt.The measuring space (14) is gas-permeable from the sample space (10) Separated membrane (11). The membrane (11) is in the invention Example a thermally stable membrane made of steam sterilizable Material is made. According to the invention, polytetrafluoroethylene is used for this and / or silicone preferred.

    Das gelöste Gas diffundiert durch die Membran (11) in den Probenraum (10) bis zur Einstellung eines Gleichgewichtes. Da die Diffusion von Gasen durch eine Membran partialdruckkontrolliert ist, bestimmt die Sonde (1) den Partialdruck. Damit mißt die Sonde einen biologisch bedeutsamen Parameter; denn die Versorgung der Microorganismen ist, wie alle Transportvorgänge aus den Zellen bzw. in die Zellen, partialdruck- und nicht konzentrationskontrolliert.The dissolved gas diffuses through the membrane (11) into the sample space (10) until equilibrium is reached. Because the diffusion of Gases controlled by a partial pressure membrane determines the Probe (1) the partial pressure. So the probe measures you biologically significant parameter; because the supply of the microorganisms is like all transport processes from the cells or into the cells, partial pressure and not concentration controlled.

    Die Lumineszenzdiode (6) emittiert schmalbandiges Licht, das selektiv durch das zu bestimmende Gas absorbiert wird. Die Wellenlänge kann in bezug auf das zu untersuchende Gas sowohl im UV/VIS als auch im Infrarotbereich liegen. Für Kohlendioxid sind dies vorzugsweise 4,3 µm. The luminescent diode (6) emits narrowband light that is selective is absorbed by the gas to be determined. The wavelength can be in with regard to the gas to be examined in both UV / VIS and in Infrared range. For carbon dioxide this is preferably 4.3 µm.

    Der emittierte Wellenlängenbereich kann beschränkt sein durch einen Wärmenstrahler mit Interferenzfilter oder vorzugsweise durch eine schmalbandige Lumineszenzdiode. Der besondere Vorteil beim Einsatz der Luminessenzdiode ist, daß die Strahlung moduliert werden kann, was die Detektion erhöht und Effekte wie Gleichstromdrift minimiert.The emitted wavelength range can be limited by one Heat radiator with interference filter or preferably through a narrow band luminescent diode. The particular advantage in use the luminescence diode is that the radiation can be modulated what detection is increased and effects such as DC drift are minimized.

    Die emittierte Strahlung wird über den Lichtwellenleiter (12) dem Meßraum zugeführt. Das vorhandene Gas schwächt spezifisch die emittierte Strahlung ab. Das abgeschwächte Licht wird zum Teil vom Lichtwellenleiter (13) aufgenommen und dem Fotoempfänger (7) zugeführt. Dieser mißt das abgeschwächte Licht und produziert ein elektrisches Signal proportional zum abgeschwächten Licht. Wenn moduliertes Licht eingesetzt wird, läßt sich das elektrische Signal ebenfalls modulieren.The emitted radiation is the via the optical waveguide (12) Measuring room fed. The gas present specifically weakens it emitted radiation. The weakened light is partly from the Optical waveguide (13) recorded and the photo receiver (7) fed. This measures the weakened light and produces electrical signal proportional to the attenuated light. If modulated light is used, the electrical signal also modulate.

    Die Länge der Meßkammer (14) entspricht der optischen Weglänge. Eine optimale optische Weglänge wird im Meßraum (14) so gewählt, daß die Sonde (1) den gesamten Meßbereich erfaßt. Der Meßbereich ist umgekehrt proportional zur Weglänge. Je kleiner somit die Weglänge der Meßkammer (14) der Sonde (1) ist, desto größer ist der detektierbare Bereich und desto kleiner ist die Auflösung.The length of the measuring chamber (14) corresponds to the optical path length. A optimal optical path length is selected in the measuring room (14) so that the Probe (1) covers the entire measuring range. The measuring range is inversely proportional to the path length. The smaller the path length of the Measuring chamber (14) of the probe (1), the larger the detectable Area and the smaller the resolution.

    Die mit der Erfindung erzielten Vorteile bestehen insbesondere darin, daß vor allem im Fall der Kohlendioxidpartialdruckmessung durch Trennung des Meßraumes vom Probenraum nicht durch die Anwesenheit von trübenden und sich in ihrer Konzentration ändernden Partikeln Einflüsse entstehen. Des weiteren wird durch die Implementierung der Membran die Messung des Partialdrucks garantiert. Es ist zwar prinzipiell möglich, mit Hilfe des Henry'schen Gesetzes Konzentration in Partialdrücke umzurechnen. Doch erfordert es die gleichzeitige Kenntnis von Temperatur und Druck sowie der Medieneigenschaften. Letzteres ist insbesondere bei der Anwendung von Fermentationsmedien schwierig. Weiterhin werden die Langzeitstabilität, Genauigkeit und der Meßbereich gegenüber pHsensitiven Partialdrucksonden erhöht.The advantages achieved by the invention are in particular that especially in the case of carbon dioxide partial pressure measurement by separation of the measuring room from the sample room not by the presence of clouding and changing their concentration arise. Furthermore, through the implementation of the membrane Measurement of partial pressure guaranteed. In principle it is possible to use Using Henry's law to convert concentration into partial pressures. But it requires the simultaneous knowledge of temperature and Pressure as well as the media properties. The latter is particularly the case with Difficult to use fermentation media. Furthermore, the Long-term stability, accuracy and the measuring range compared to pH-sensitive Partial pressure probes increased.

    Die erfindungsgemäße Sonde ist sowohl in der Getränkeindustrie als auch in der Biotechnologie besonders gut einsetzbar. Für den Einsatz in der Lebensmitteltechnologie lassen sich Sonden für Meßbereiche von bis zu 10 bar erstellen.The probe according to the invention is both in the beverage industry Can also be used particularly well in biotechnology. For use in In food technology, probes for measuring ranges from to to create 10 bar.

    Beim Einsatz für die Kohlendioxidpartialdruckmessung im Bereich der Fermentationstechnik ist von Vorteil, daß eine Vorkalibrierung möglich ist. Denn aufgrund des inhibierenden Einflusses von Kohlendioxid auf die meisten Organismen kann eine Nachkalibrierung nicht mehr vorgenommen werden. Vorteilhaft in diesem Anwendungsbereich ist darüber hinaus, daß die Sonde während der Sterilisation thermischen Belastungen standhält und Temperaturen von 150°C ohne weiteres zu widerstehen vermag. Schließlich ist von Vorteil, daß im Gegensatz zu den bisherigen Verfahren mit Absorptionsmessung eine Störung durch Stoffe, die ebenfalls im infraroten Bereich absorbieren, ausgeschlossen ist.When used for carbon dioxide partial pressure measurement in the area of Fermentation technology is advantageous in that a pre-calibration is possible. Because of the inhibitory influence of carbon dioxide on the Most organisms can no longer be recalibrated become. It is advantageous in this area of application addition, that the probe is thermal during sterilization Withstands loads and temperatures of 150 ° C without further ado can withstand. Finally, it is an advantage that, in contrast to the previous methods with absorption measurement a disturbance by substances, which also absorb in the infrared range is excluded.

    Claims (18)

    1. Device for measuring the partial pressure of gases dissolved in liquids, comprising
      a) a measuring chamber (14) which is separated, by means of a gas-permeable membrane (11) which is permeable to the gas to be determined, from a sample space (19) [sic] which contains the liquid and, dissolved therein, the gas to be determined,
      b) a light-emission source (6) for generating a light beam which passes through the measuring chamber (14) and has a wavelength which is absorbed by the gas to be determined,
      c) a measuring arrangement (7) for determining the light beam emerging from the measuring chamber (14),
      characterized in that
      d) the measuring chamber (14) is filled with a chemically and biologically inert fluid for absorbing the gas to be determined.
    2. Device according to Claim 1, characterized in that the measuring chamber (14), the light-emission source (6) and the measuring arrangement (7) are arranged in a rod-shaped probe (1).
    3. Device according to Claim 2, characterized in that the probe (1) is sterilizable.
    4. Device according to Claim 3, characterized in that the probe (1) can be sterilized using steam.
    5. Device according to Claims 1 to 4, characterized in that the membrane consists of polytetrafluoroethylene.
    6. Device according to Claims 1 to 5, characterized in that the membrane is a gas-selective solubility membrane, through which equilibrium is established between the sample space (10) and the measuring chamber (14).
    7. Device according to one of Claims 1 to 6, characterized in that the fluid is a liquid.
    8. Device according to one of Claims 1 to 6, characterized in that the fluid is a gas.
    9. Device according to Claims 1 to 7, characterized in that it contains an optical waveguide (12) for guiding the light beam from the light-emission source (6) to the measuring chamber (14) and an optical waveguide (13) for guiding the light from the measuring chamber (14) to the measuring arrangement (7).
    10. Device according to Claims 1 to 9, characterized in that the light-emission source (6) is a light-emitting diode.
    11. Device according to Claims 1 to 10, characterized in that the measuring arrangement (7) is a photodiode, a photoresistor or a lead selenide photodetector.
    12. Device according to Claims 1 to 11, characterized in that the measuring arrangement (7) is connected to a circuit arrangement for evaluating, storing and displaying the signals.
    13. Device according to Claims 1 to 12, characterized in that it is of pressure-proof design.
    14. Device according to Claim 13, characterized in that [lacuna] is designed for operation under pressures of up to 200 bar, preferably up to 20 bar.
    15. Method for measuring the partial pressure of gases dissolved in liquids using a device according to one of Claims 1 to 14, characterized in that
      a) the membrane (11) of this device is immersed in the liquid present in the sample space (10),
      b) the gas which is present in the liquid and is to be determined diffuses into the measuring chamber (14) through the membrane (11),
      c) a light beam having a wavelength which is absorbed by the gas to be determined is guided through the measuring chamber (14), and
      d) the unabsorbed light is fed to the measuring arrangement (7).
    16. Method according to Claim 15, characterized in that the measurement is carried out using infrared radiation.
    17. Use of the device according to one of Claims 1 to 14 for determining the partial pressure of oxygen or carbon dioxide.
    18. Use of the device according to one of Claims 1 to 14 for measuring, controlling and regulating fermentation processes, methods for the production of drinks, and waste-water purification plants.
    EP95942708A 1994-12-21 1995-12-20 Device for measuring the partial pressure of gases dissolved in liquids Expired - Lifetime EP0871865B1 (en)

    Applications Claiming Priority (3)

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    DE4445668A DE4445668C2 (en) 1994-12-21 1994-12-21 Device for measuring the partial pressure of gases dissolved in liquids in systems for carrying out biotechnological or food technology processes
    DE4445668 1994-12-21
    PCT/EP1995/005050 WO1996019723A2 (en) 1994-12-21 1995-12-20 Device for measuring the partial pressure of gases dissolved in liquids

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    EP0871865A2 EP0871865A2 (en) 1998-10-21
    EP0871865B1 true EP0871865B1 (en) 2003-02-19

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    JP (1) JPH10512668A (en)
    AT (1) ATE232977T1 (en)
    AU (1) AU695408B2 (en)
    CA (1) CA2208597A1 (en)
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    JPH10512668A (en) 1998-12-02
    WO1996019723A2 (en) 1996-06-27
    AU4388196A (en) 1996-07-10
    DE19624844A1 (en) 1998-01-02
    DE4445668A1 (en) 1996-06-27
    DE59510559D1 (en) 2003-03-27
    WO1996019723A3 (en) 1996-08-22
    CA2208597A1 (en) 1996-06-27
    DE4445668C2 (en) 1997-05-15
    AU695408B2 (en) 1998-08-13
    DE19624844C2 (en) 1999-12-16
    ATE232977T1 (en) 2003-03-15
    EP0871865A2 (en) 1998-10-21

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